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fd: use atomics to manage fd_refcnt and fd_holcnt

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This gets rid of fdesc_mtx.
This commit is contained in:
Mateusz Guzik 2015-06-10 09:34:50 +00:00
parent 5cd7a4f76c
commit 153cc61b54
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=284211
2 changed files with 28 additions and 30 deletions
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54
sys/kern/kern_descrip.c
View File

@ -1809,8 +1809,8 @@ fdinit(struct filedesc *fdp, bool prepfiles)
/* Create the file descriptor table. */
FILEDESC_LOCK_INIT(newfdp);
newfdp->fd_refcnt = 1;
newfdp->fd_holdcnt = 1;
refcount_init(&newfdp->fd_refcnt, 1);
refcount_init(&newfdp->fd_holdcnt, 1);
newfdp->fd_cmask = CMASK;
newfdp->fd_map = newfdp0->fd_dmap;
newfdp->fd_lastfile = -1;
@ -1852,24 +1852,19 @@ fdhold(struct proc *p)
{
struct filedesc *fdp;
mtx_lock(&fdesc_mtx);
PROC_LOCK_ASSERT(p, MA_OWNED);
fdp = p->p_fd;
if (fdp != NULL)
fdp->fd_holdcnt++;
mtx_unlock(&fdesc_mtx);
refcount_acquire(&fdp->fd_holdcnt);
return (fdp);
}
static void
fddrop(struct filedesc *fdp)
{
int i;
if (fdp->fd_holdcnt > 1) {
mtx_lock(&fdesc_mtx);
i = --fdp->fd_holdcnt;
mtx_unlock(&fdesc_mtx);
if (i > 0)
if (refcount_release(&fdp->fd_holdcnt) == 0)
return;
}
@ -1884,9 +1879,7 @@ struct filedesc *
fdshare(struct filedesc *fdp)
{
FILEDESC_XLOCK(fdp);
fdp->fd_refcnt++;
FILEDESC_XUNLOCK(fdp);
refcount_acquire(&fdp->fd_refcnt);
return (fdp);
}
@ -2032,6 +2025,7 @@ fdclearlocks(struct thread *td)
void
fdescfree(struct thread *td)
{
struct proc *p;
struct filedesc0 *fdp0;
struct filedesc *fdp;
struct freetable *ft, *tft;
@ -2040,31 +2034,29 @@ fdescfree(struct thread *td)
struct vnode *cdir, *jdir, *rdir;
int i;
fdp = td->td_proc->p_fd;
p = td->td_proc;
fdp = p->p_fd;
MPASS(fdp != NULL);
#ifdef RACCT
if (racct_enable) {
PROC_LOCK(td->td_proc);
racct_set(td->td_proc, RACCT_NOFILE, 0);
PROC_UNLOCK(td->td_proc);
PROC_LOCK(p);
racct_set(p, RACCT_NOFILE, 0);
PROC_UNLOCK(p);
}
#endif
if (td->td_proc->p_fdtol != NULL)
fdclearlocks(td);
mtx_lock(&fdesc_mtx);
td->td_proc->p_fd = NULL;
mtx_unlock(&fdesc_mtx);
PROC_LOCK(p);
p->p_fd = NULL;
PROC_UNLOCK(p);
if (refcount_release(&fdp->fd_refcnt) == 0)
return;
FILEDESC_XLOCK(fdp);
i = --fdp->fd_refcnt;
if (i > 0) {
FILEDESC_XUNLOCK(fdp);
return;
}
cdir = fdp->fd_cdir;
fdp->fd_cdir = NULL;
rdir = fdp->fd_rdir;
@ -2884,7 +2876,9 @@ mountcheckdirs(struct vnode *olddp, struct vnode *newdp)
nrele = 0;
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
PROC_LOCK(p);
fdp = fdhold(p);
PROC_UNLOCK(p);
if (fdp == NULL)
continue;
FILEDESC_XLOCK(fdp);
@ -2979,9 +2973,13 @@ sysctl_kern_file(SYSCTL_HANDLER_ARGS)
n = 0;
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
if (p->p_state == PRS_NEW)
PROC_LOCK(p);
if (p->p_state == PRS_NEW) {
PROC_UNLOCK(p);
continue;
}
fdp = fdhold(p);
PROC_UNLOCK(p);
if (fdp == NULL)
continue;
/* overestimates sparse tables. */
@ -3008,8 +3006,8 @@ sysctl_kern_file(SYSCTL_HANDLER_ARGS)
}
xf.xf_pid = p->p_pid;
xf.xf_uid = p->p_ucred->cr_uid;
PROC_UNLOCK(p);
fdp = fdhold(p);
PROC_UNLOCK(p);
if (fdp == NULL)
continue;
FILEDESC_SLOCK(fdp);

4
sys/sys/filedesc.h
View File

@ -83,8 +83,8 @@ struct filedesc {
int fd_lastfile; /* high-water mark of fd_ofiles */
int fd_freefile; /* approx. next free file */
u_short fd_cmask; /* mask for file creation */
u_short fd_refcnt; /* thread reference count */
u_short fd_holdcnt; /* hold count on structure + mutex */
int fd_refcnt; /* thread reference count */
int fd_holdcnt; /* hold count on structure + mutex */
struct sx fd_sx; /* protects members of this struct */
struct kqlist fd_kqlist; /* list of kqueues on this filedesc */
int fd_holdleaderscount; /* block fdfree() for shared close() */